KR102452946B1 - Gas diffusion layer for metal air battery, metal air battery and method of manufacturing the same - Google Patents

Abstract

According to the metal-air battery according to the embodiment, including a negative electrode metal layer, an electrolyte membrane, a positive electrode layer and a gas diffusion layer, the positive electrode layer may have a plurality of insertion grooves into which some regions of a plurality of carbon fibers of the gas diffusion layer are inserted. have.

Description

A gas diffusion layer for a metal-air battery, a metal-air battery including the same, and a method for manufacturing the same

It relates to a gas diffusion layer for a metal-air battery, a metal-air battery including the same, and a method for manufacturing the same. Specifically, it relates to a gas diffusion layer for a metal-air battery having improved energy density, a metal-air battery including the same, and a method for manufacturing the same.

A metal-air battery is a battery including a negative electrode capable of occluding/releasing ions and a positive electrode using oxygen in the air as an active material. In the case of a metal-air battery, a reduction/oxidation reaction of oxygen introduced from the outside occurs at the anode, and an oxidation/reduction reaction of metal occurs at the cathode, and chemical energy generated at this time is extracted as electrical energy. For example, metal-air cells absorb oxygen when discharging and release oxygen when charging. As described above, since the metal-air battery uses oxygen present in the atmosphere, the energy density of the battery can be dramatically improved. For example, a metal-air battery may have an energy density several times higher than that of a conventional lithium ion battery.

In addition, the metal-air battery has excellent stability because the possibility of ignition due to abnormal high temperature is low, and since it operates only by absorption/release of oxygen without the need to use heavy metal, the possibility of causing environmental pollution is also low. Due to these various advantages, a lot of research on metal-air batteries is currently being made.

According to the embodiment, a gas diffusion layer for a metal-air battery capable of improving energy density by reducing the weight per unit area of the gas diffusion layer, a metal-air battery including the same, and a manufacturing method thereof are provided.

Metal-air battery according to an embodiment,

at least one positive electrode layer using oxygen as an active material and having a first surface and a second surface opposite to the first surface;

a gas diffusion layer disposed on the first surface of the anode layer and including a plurality of carbon fibers;

an electrolyte membrane disposed on the second surface of the anode layer; and

Including; a negative electrode metal layer disposed on the electrolyte membrane;

The anode layer may have a plurality of insertion grooves into which some regions of the plurality of carbon fibers are inserted.

The average depth of the insertion groove may be 20% to 60% of the diameter of the carbon fiber.

The average width of the insertion groove may be 80% to 100% of the diameter of the carbon fiber.

The average length of the insertion groove may be 3 mm or more.

An average distance between the insertion grooves may be 30 μm to 1000 μm.

The carbon fiber may have a diameter of 5 μm to 10 μm.

The weight per unit area of the gas diffusion layer is 0.5 mg/cm ² may be below.

The weight per unit area of the gas diffusion layer is 0.007 mg/cm ² may be more than

The gas diffusion layer includes a first carbon fiber layer having a plurality of carbon fibers disposed on the positive electrode layer, and a first carbon fiber layer disposed on the first carbon fiber layer in a direction crossing the extending direction of the carbon fibers of the first carbon fiber layer. and a second carbon fiber layer having a plurality of elongated carbon fibers.

The gas diffusion layer, as a single layer, may be bent to face each other.

The gas diffusion layer may have a plurality of carbon fiber layers including a plurality of carbon fibers, and the plurality of carbon fiber layers may be four or less.

The gas diffusion layer is partially disposed on the anode layer, and the cathode metal layer, the electrolyte membrane and the anode layer are bent over the gas diffusion layer so that the anode layer is in contact with three surfaces of the gas diffusion layer, and the gas diffusion layer One side of the is exposed to the outside.

Metal-air battery manufacturing method according to an embodiment,

disposing a plurality of carbon fibers on one surface of the positive electrode layer using oxygen as an active material; and

pressing the plurality of carbon fibers toward the positive electrode layer such that a partial region of the plurality of carbon fibers is inserted into one surface of the positive electrode layer to form an insertion groove.

In the pressing step of the carbon fiber, the carbon fiber may be pressed to the positive electrode layer such that the average depth of the insertion groove is 20% to 60% of the diameter of the carbon fiber.

In the pressing step of the carbon fiber, the carbon fiber may be pressed so that the average width of the insertion groove is 80% to 100% of the diameter of the carbon fiber.

In the disposing of the carbon fibers, a plurality of carbon fibers may be arranged such that the average distance between the carbon fibers is 30 μm to 1000 μm.

The weight per unit area of the gas diffusion layer is 0.5 mg/cm ² may be below.

The weight per unit area of the gas diffusion layer is 0.007 mg/cm ² may be more than

A gas diffusion layer for a metal-air battery according to an embodiment,

A gas diffusion layer comprising a plurality of carbon fibers disposed on one surface of a positive electrode layer using oxygen as an active material,

A partial region of the plurality of carbon fibers may be inserted into one surface of the positive electrode layer.

The gas diffusion layer does not include a binder.

According to the gas diffusion layer for a metal-air battery according to an embodiment of the present invention as described above, a metal-air battery including the same, and a method for manufacturing the same, by inserting and fixing a portion of carbon fibers into the positive electrode layer so as not to contain a binder, the gas diffusion layer It is possible to reduce the weight per unit area, thereby improving the energy density of the metal-air battery.

1 is a cross-sectional view showing an example of a metal-air battery according to the embodiment.
Figure 2 is a view for explaining a gas diffusion layer according to an embodiment, a partial enlarged view of Figure 1,
FIG. 3 is a view for explaining an anode layer according to an embodiment, in which a gas diffusion layer is omitted from FIG. 2 .
4A is a plan view for explaining a gas diffusion layer according to an embodiment, and FIG. 4B is a plan view for explaining a gas diffusion layer according to another embodiment.
5 is a graph showing the voltage loss according to the weight per unit area of the gas diffusion layer.
6 is a cross-sectional view illustrating an example of a metal-air battery according to another embodiment.
7 is a view for explaining a gas diffusion layer according to an embodiment, and is a partially enlarged view of FIG. 6 .
8A is a plan view illustrating a gas diffusion layer according to an exemplary embodiment, and FIG. 8B is a plan view illustrating a gas diffusion layer according to another exemplary embodiment.
9 is a perspective view illustrating an example of a metal-air battery according to another embodiment.
10A is a plan view for explaining a gas diffusion layer according to an embodiment, FIG. 10B is a plan view for explaining a gas diffusion layer according to another embodiment, and FIG. 10C is a plan view for explaining a gas diffusion layer according to another embodiment to be.
11A and 11B are perspective views illustrating another example of a metal-air battery according to another embodiment.
12 is a flowchart illustrating a method of manufacturing a metal-air battery according to an embodiment;
13A to 13B are diagrams for conceptually explaining a method of manufacturing a metal-air battery.
14 is a view of an anode layer manufactured according to a method of manufacturing a metal-air battery observed with an electron microscope.
15 is a graph showing discharge capacities of metal-air batteries according to Comparative Examples 1 and 2 and Examples 1, 2, and 3;

Hereinafter, a gas diffusion layer for a metal-air battery, a metal-air battery, and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numbers refer to the same components, and the size or thickness of each component may be exaggerated for convenience of description. Meanwhile, the embodiments described below are merely exemplary, and various modifications are possible from these embodiments.

1 is a cross-sectional view showing an example of a metal-air battery 1 according to the embodiment. FIG. 2 is a view for explaining the gas diffusion layer 14 according to an embodiment, and is a partial enlarged view of FIG. 1 , and FIG. 3 is a view for explaining the anode layer 13 according to an embodiment, FIG. 2 It is a view in which the gas diffusion layer 14 is omitted. 4A is a plan view for explaining the gas diffusion layer 14 according to an embodiment, and FIG. 4B is a plan view for explaining the gas diffusion layer 14A according to another embodiment.

Referring to FIG. 1 , the metal-air battery 1 may have a two-dimensional planar structure. For example, the metal-air battery 1 has a negative electrode metal layer 11, an electrolyte membrane 12, a positive electrode layer 13, and a gas diffusion layer 14 for a metal-air battery (hereinafter referred to as a 'gas diffusion layer 14'). They may be sequentially stacked. The metal-air cell 1 may further include a casing (not shown) surrounding the rest of the metal-air cell 1 except for the upper surface of the gas diffusion layer 14 .

The anode metal layer 11 serves to occlude/release metal ions, for example, lithium (Li), sodium (Na), zinc (Zn), potassium (K), calcium (Ca), and magnesium (Mg). , iron (Fe), aluminum (Al), or an alloy thereof may be used.

The electrolyte membrane 12 serves to transfer metal ions to the anode layer 13 . The electrolyte membrane 12 may be referred to as a negative electrolyte membrane. To this end, the electrolyte membrane 12 may include an electrolyte formed by dissolving a metal salt in a solvent. The electrolyte may be a solid phase including a polymer electrolyte, an inorganic electrolyte, or a composite electrolyte in which they are mixed.

The electrolyte membrane 12 may be manufactured to be flexible. For example, as a metal salt, LiN(SO ₂ CF ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiClO ₄ , LiBF ₄ , LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , LiN(SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlCl ₄ or LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide) may be used, and other metal salts such as AlCl ₃ , MgCl ₂ , NaCl, KCl, NaBr, KBr, CaCl ₂ and the like may be further added to the above-described lithium salt. As the solvent, any material capable of dissolving these lithium salts and metal salts may be used.

In addition, the electrolyte membrane 12 may further include a separator having conductivity with respect to metal ions while preventing the permeation of oxygen. As the separator, a flexible polymer-based separator may be used. For example, as the separator, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a porous film made of an olefin resin such as polyethylene or polypropylene may be used. Although the separator and the electrolyte may be formed as separate layers, the electrolyte membrane 12 may be formed as a single layer by impregnating the electrolyte in the pores of the porous separator. For example, the electrolyte membrane 12 may be formed by impregnating the electrolyte formed by mixing polyethylene oxide (PEO) and LiTFSI in the pores of the porous separator.

The anode layer 13 may include an electrolyte for conduction of metal ions, a catalyst for oxidation/reduction of oxygen, a conductive material, and a binder. For example, the positive electrode layer 13 may be formed by mixing the above-described electrolyte, catalyst, conductive material and binder, adding a solvent to prepare a positive electrode slurry, coating the electrolyte on the electrolyte membrane 12 and drying the mixture.

Here, the electrolyte may include the lithium salt or the metal salt described above. As the conductive material, for example, a porous carbon-based material, a conductive metal material, or a conductive organic material may be used, or a mixture thereof may be used. For example, carbon black, graphite, graphene, activated carbon, carbon fibers, carbon nanotubes, or the like can be used as the carbon-based material. The conductive metal material can be used, for example, in the form of a metal powder. As the catalyst, for example, platinum (Pt), gold (Au), silver (Ag), etc. can be used, or oxides such as manganese (Mn), nickel (Ni), cobalt (Co) can be used. . In addition, as the binder, for example, polytetrafluoroethylene (PTFE), polypropylene, polyvinylidene fluoride (PVDF), polyethylene, styrene-butadiene rubber, or the like can be used.

The anode layer 13 has a first surface 131 and a second surface 132 opposite to the first surface 131 . The gas diffusion layer 14 is disposed on the first surface 131 of the anode layer 13 , and the electrolyte membrane 12 is disposed on the second surface 132 .

The gas diffusion layer 14 serves to absorb oxygen in the atmosphere and provide it to the anode layer 13 . To this end, the gas diffusion layer 14 may have a structure in which external oxygen can smoothly move and diffuse. For example, the gas diffusion layer 14 may have a flow path structure.

The gas diffusion layer 14 may have conductivity. For example, the gas diffusion layer 14 may include a plurality of carbon fibers 141 . The plurality of carbon fibers 141 may be fibers having a main component of carbon and having a diameter of 20 μm or less. As an example, the diameter of the carbon fibers 141 may be 5 μm to 10 μm.

The carbon fibers 141 may be referred to as graphite fibers. The carbon fiber 141 may be a hollow carbon fiber.

The length of the carbon fiber 141 may be 3 mm or more. The length of the plurality of carbon fibers 141 may be 1000 mm or less.

Based on the length of the anode layer 13 on which the gas diffusion layer 14 is disposed, the length of the carbon fiber 141 may be determined. For example, when the length of the anode layer 13 is long, a long carbon fiber 141 may be used, and when the length of the anode layer 13 is short, a short carbon fiber 141 may be used. .

The weight of the gas diffusion layer 14 may be less than 19% of the total weight of the metal-air cell 1 . To this end, the gas diffusion layer 14 according to the embodiment may not include a binder. Since the gas diffusion layer 14 does not include a binder, the weight per unit area may be reduced. For example, the weight per unit area of the gas diffusion layer 14 is 0.5 mg/cm ² may be below.

On the other hand, as described above, since the gas diffusion layer 14 of the present application does not include a binder, when arranging a plurality of carbon fibers 141 on the first surface 131 of the positive electrode layer 13 without a separate measure , the plurality of carbon fibers 141 may not be fixed to the anode layer 13 during the manufacturing process and may be scattered or moved.

In consideration of this point, referring to FIGS. 2 and 3 , in the metal-air battery 1 according to the embodiment, a plurality of carbon fibers 141 can be fixed on the positive electrode layer 13 , a plurality of carbon A portion of the fiber 141 may be inserted into the anode layer 13 . Accordingly, the anode layer 13 may have an insertion groove 133 into which a partial region of the carbon fiber 141 is inserted. As described above, by inserting a partial region of the carbon fibers 141 of the gas diffusion layer 14 into the insertion groove 133 of the anode layer 13 , the gas diffusion layer 14 may be fixed to the anode layer 13 .

The insertion groove 133 of the anode layer 13 may have a depth, width, length, and spacing in which the carbon fibers 141 of the gas diffusion layer 14 can be fixed to the anode layer 13 and sufficient oxygen supply and diffusion are possible. have.

For example, the average depth d of the insertion groove 133 may be 20% to 60% of the diameter of the carbon fiber 141 . When the diameter of the carbon fiber 141 is 7 μm, the average depth d of the insertion groove 133 may be 1.4 μm or more.

For example, the average width w of the insertion groove 133 may be 80% to 100% of the diameter of the carbon fiber 141 . The average length of the insertion groove 133 may be 3 mm or more. The average spacing g between the plurality of insertion grooves 133 may be 30 μm to 1000 μm. The gas diffusion layer 14 includes a first space occupied by the carbon fibers 141 and a second space in which the carbon fibers 141 are not disposed and in which oxygen gas can move and diffuse. A ratio of the second space in the gas diffusion layer 14 may be 80% to 99%.

The gas diffusion layer 14 may have a single layer structure. For example, the plurality of carbon fibers 141 may be arranged as one layer on the anode layer 13 .

Referring to FIG. 4A , the plurality of carbon fibers 141 may extend in a predetermined direction and may be arranged to be spaced apart from each other. However, the arrangement of the plurality of carbon fibers 141 is not limited thereto, and may be arranged in various ways. For example, as shown in FIG. 4B , the plurality of carbon fibers 141 of the gas diffusion layer 14A extend in various directions and may be arranged such that at least some of them are spaced apart.

As described above, in the gas diffusion layers 14 and 14A according to the embodiment, by inserting and fixing a plurality of carbon fibers 141 into the insertion grooves 133 of the positive electrode layer 13 without a separate binder, the weight per unit area 0.5 mg/cm ² It can be reduced to be less than, and it is possible to increase the energy density of the metal-air battery (1).

However, when the weight per unit area of the gas diffusion layer 14 is too small, the voltage loss due to the resistance of ohms may be large enough to affect the metal-air battery 1 .

5 is a graph showing the voltage loss according to the weight per unit area of the gas diffusion layer 14 . Referring to FIG. 5 , it can be seen that when the weight per unit area of the gas diffusion layer 14 decreases to less than a predetermined section, the voltage loss rapidly increases. Accordingly, in the gas diffusion layer 14 according to the embodiment, the weight per unit area of the gas diffusion layer 14 is 0.007 mg/cm ² so that the voltage loss due to the ohmic resistance becomes 1 mV or less in consideration of this voltage loss. may be more than

6 is a cross-sectional view illustrating an example of a metal-air battery 1B according to another embodiment. 7 is a view for explaining the gas diffusion layer 14B according to an embodiment, and is a partially enlarged view of FIG. 6 . 8A is a plan view for explaining the gas diffusion layer 14B according to an embodiment, and FIG. 8B is a plan view for explaining the gas diffusion layer 14C according to another embodiment.

6 and 7 , the metal-air battery 1B according to the embodiment may include a negative electrode metal layer 11 , an electrolyte membrane 12 , a positive electrode layer 13 , and a gas diffusion layer 14B. The same reference numerals are used for the same components as those of the above-described embodiment, and repeated descriptions are omitted.

The gas diffusion layer 14B has a two-layer structure, and each of the carbon fiber layers 140 and 150 may include a plurality of carbon fibers 141 and 151 . Each of the carbon fiber layers 140 and 150 does not include a binder. In the gas diffusion layer 14B having a two-layer structure, a plurality of carbon fibers 141 and 151 may be arranged in a lattice form. For example, the gas diffusion layer 14B includes a first carbon fiber layer 140 in which some regions of the plurality of carbon fibers 141 are inserted into the insertion groove 133 of the first surface 131, and a plurality of carbon fibers ( 151 ) may include a second carbon fiber layer 150 extending in a direction crossing the extending direction of the carbon fibers 141 of the first carbon fiber layer 140 on the first carbon fiber layer 140 .

As an example, as shown in FIG. 8A , in the gas diffusion layer 14B, a plurality of carbon fibers 141 and 151 of each carbon fiber layer 140 and 150) may be arranged in a predetermined direction. As another example, as shown in FIG. 8B , in the gas diffusion layer 14C, a plurality of carbon fibers 141 and 151 of each carbon fiber layer 140 and 150 may be arranged in various directions.

Meanwhile, in FIG. 7 , the carbon fibers 151 of the second carbon fiber layer 150 are illustrated as being spaced apart from the anode layer 13 , but the present invention is not limited thereto. For example, although not shown, a portion of the carbon fiber 151 of the second carbon fiber layer 150 is disposed on the carbon fiber 141 of the first carbon fiber layer 140 and is not inserted into the anode layer 13 . However, other partial regions of the carbon fibers 151 of the second carbon fiber layer 150 may be inserted into the anode layer 13 exposed between the carbon fibers 141 of the first carbon fiber layer 140 .

The layer structure of the gas diffusion layers 14B and 14C may be two or less. If the layer structure of the gas diffusion layers 14B and 14C is three or more, since there is no binder for fixing the position between the carbon fibers 141 and 151, the carbon fibers having three or more layers are not inserted into the anode layer 13. and the position may not be fixed accordingly. On the other hand, if the layer structure of the gas diffusion layers 14B and 14C has two or less layers, even if there is no binder for fixing the position between the carbon fibers 141 and 151, the carbon fibers 141 and 151 with two or less layers are anodes. The layer 13 may be inserted and supported.

9 is a perspective view illustrating an example of a metal-air battery 1C according to another embodiment. 10A is a plan view for explaining the gas diffusion layer 14 according to an embodiment, FIG. 10B is a plan view for explaining the gas diffusion layer 14C according to another embodiment, and FIG. 10C is a gas according to another embodiment It is a plan view for demonstrating the diffusion layer 14E.

Referring to FIG. 9 , the structure of the metal-air battery 1C may include an anode metal layer 11 , an electrolyte membrane 12 , a cathode layer 13 , and a gas diffusion layer 14D. The same reference numerals are used for the same components as those of the above-described embodiments, and repeated descriptions are omitted.

The metal-air battery 1 according to the embodiment may have a three-dimensional shape. The metal-air battery 1C may have a structure in which the negative electrode metal layer 11 , the electrolyte membrane 12 , and the positive electrode layer 13 are bent.

As an example, referring to FIG. 10A , the gas diffusion layer 14 may have a single layer structure in which a plurality of carbon fibers 141 are arranged on the anode layer 13 . Some regions of the plurality of carbon fibers 141 may be inserted into the plurality of insertion grooves 133 of the anode layer 13 . The gas diffusion layer 14 may be folded along the bending predetermined line FL to become the gas diffusion layer 14D having a structure facing each other as shown in FIG. 9 . The bent gas diffusion layer 14D may have a two-layer structure.

As another example, referring to FIG. 10B , the gas diffusion layer 14C includes a first carbon fiber layer 140 in which a plurality of carbon fibers 141 are arranged on the anode layer 13 , and a plurality of carbon fibers 151 . It may include a second carbon fiber layer 150 arranged on the first carbon fiber layer 140 . The carbon fibers 141 of the first carbon fiber layer 140 and the carbon fibers 151 of the second carbon fiber layer 150 may be disposed to cross each other. The gas diffusion layer 14C may be bent along the predetermined bending line FL to become the gas diffusion layer 14D having a structure facing each other. The bent gas diffusion layer 14D may have a structure of four or less layers.

As another example, referring to FIG. 10C , the gas diffusion layer 14E may be partially disposed on the anode layer 13 . The cathode metal layer 11, the electrolyte membrane 12, and the anode layer 13 are bent over the gas diffusion layer 14E so that the anode layer 13 is in contact with three surfaces of the gas diffusion layer 14, and the gas diffusion layer 14E ) may be exposed to the outside. The gas diffusion layer 14E may have a structure of two or less layers.

Meanwhile, in the above-described embodiments, as an example of the metal-air battery 1C having a three-dimensional shape, it has one gas diffusion layer 14D, and the anode metal layer 11 , the electrolyte membrane 12 and the anode layer 13 . This one-time bending structure was mainly described. However, the metal-air battery 1 having a three-dimensional shape is not limited thereto, and may be variously modified. As an example, the metal-air battery 1D includes a plurality of gas diffusion layers 14D, as shown in FIG. 11A , and has a structure in which the anode metal layer 11, the electrolyte membrane 12, and the cathode layer 13 are bent multiple times. can have As another example, in the metal-air battery 1E, as shown in FIG. 11B , a plurality of battery cells 10 are arranged in the vertical direction, and each battery cell 10 has one gas diffusion layer 14D and a negative electrode metal layer 11 ), the electrolyte membrane 12 and the anode layer 13 may have a structure in which they are bent once.

12 is a flowchart illustrating a method of manufacturing the metal-air battery 1 according to the embodiment, and FIGS. 13A to 13B are diagrams for conceptually explaining the manufacturing method of the metal-air battery 1 .

12 and 13A , first, a plurality of carbon fibers 141 are disposed on the first surface 131 of the anode layer 13 ( S10 ). A plurality of carbon fibers 141 may be sprinkled on the first surface 131 of the positive electrode layer 13 . The plurality of carbon fibers 141 may be disposed such that the average distance between the plurality of carbon fibers 141 is 30 μm to 1000 μm.

The plurality of carbon fibers 141 may be fibers having a main component of carbon and having a diameter of 20 μm or less. As an example, the diameter of the carbon fibers 141 may be 5 μm to 10 μm.

The carbon fibers 141 may be referred to as graphite fibers. The carbon fiber 141 may be a hollow carbon fiber.

The length of the carbon fiber 141 may be 3 mm or more. The length of the plurality of carbon fibers 141 may be 1000 mm or less.

Based on the length of the anode layer 13 , the length of the carbon fiber 141 may be determined. For example, when the length of the anode layer 13 is long, a long carbon fiber 141 may be used, and when the length of the anode layer 13 is short, a short carbon fiber 141 may be used. .

12 and 13B, in a state in which the plurality of carbon fibers 141 are disposed on one surface of the positive electrode layer 13, the plurality of carbon fibers 141 are pressed toward the positive electrode layer 13 (S20). ). By pressing, a partial region of the plurality of carbon fibers 141 may be inserted into the first surface 131 of the anode layer 13 . Thus, in the anode layer 13 , a plurality of insertion grooves 133 into which a partial region of the carbon fiber 141 is inserted may be formed.

As an example, by pressing the carbon fibers 141 disposed on one surface of the positive electrode layer 13 using a rotatable roller R, the carbon fibers 141 may be embedded in the positive electrode layer 13 . . By rotating and moving the roller (R), the plurality of carbon fibers 141 may be pressed sequentially.

A plurality of carbon fibers 141 may be pressed so that the carbon fibers 141 of the gas diffusion layer 14 can be fixed to the anode layer 13 .

The carbon fiber 141 may be pressed toward the positive electrode layer 13 so that the average depth of the insertion groove 133 is 20% to 60% of the diameter of the carbon fiber 141 . The carbon fiber 141 may be pressed toward the positive electrode layer 13 so that the average width of the insertion groove 133 is 80% to 100% of the diameter of the carbon fiber 141 .

As described above, by disposing some regions of the plurality of carbon fibers 141 to be inserted into the anode layer 13 , the gas diffusion layer 14 supported on one surface of the anode layer 13 may be formed.

As such, since the gas diffusion layer 14 includes the conductive carbon fibers 141 and does not use a binder, the weight per unit area can be minimized. For example, the gas diffusion layer 14 has a weight per unit area of 0.5 mg/cm ² may be below. However, in consideration of voltage loss due to ohmic resistance, the weight per unit area of the gas diffusion layer 14 may be 0.007 mg/cm ² or more.

In the above-described embodiment, the method of fixing the gas diffusion layer 14 on the anode layer 13 has been mainly described with respect to the method of manufacturing the metal-air battery 1 having a two-dimensional planar structure, but the present invention is not limited thereto. It can be applied to the manufacturing method of the metal-air battery (1B, 1C, 1D, 1E) of the structure. For example, a plurality of carbon fibers 141 are pressed and bent by bending the gas diffusion layer 14 supported on the positive electrode layer 13 , the positive electrode layer 13 , the electrolyte membrane 12 , and the negative electrode metal layer 11 . The metal-air batteries 1C, 1D, and 1E having a three-dimensional structure having a fixed structure can be manufactured.

14 is a view of the anode layer 13 manufactured according to the manufacturing method of the metal-air battery 1 observed with an electron microscope.

Referring to FIG. 14 , it can be seen that an insertion groove 133 is formed on the surface of the anode layer 13 . These insertion grooves 133 may be distinguished from fine grooves generated during the manufacturing process of the anode layer 13 . The depth of the insertion groove 133 may be 1.4 μm or more. The depth of the insertion groove 133 may be 4 μm or more.

The present invention will be described in more detail through the following examples and comparative examples. However, the examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

(Manufacture of lithium air battery)

Comparative Example 1: Preparation of a conventional lithium-air battery

(Production of anode layer)

Carbon nanotubes, PTFE (polytetrafluoroethylene) binders, and positive electrolyte solutions are weighed in a predetermined weight ratio, mechanically kneaded, and then rolled to a predetermined thickness by a roll press. After fabrication, it was dried in an oven at 80° C. for 2 hours to prepare a rectangular positive electrode layer. The weight per unit area of the positive electrode layer was 2.7 mg/cm ² .

(Production of electrolyte membrane)

The separator was coated with a poly(dialyldimethylammonium-bis (trifluoromethanesulfonyl)imide) (PIL) solution containing electrolyte, and then vacuum dried (60° C., 6 h) to remove the solvent to obtain a solid electrolyte membrane. The weight per unit area of the electrolyte membrane was 2.7 mg/cm ² .

(Production of lithium-air batteries)

An electrolyte membrane was disposed on one side of the positive electrode layer, and lithium metal as a negative electrode metal layer was disposed on one side of the electrolyte membrane.

A lithium-air battery was manufactured by bending the positive electrode layer, the electrolyte membrane, and the negative electrode metal layer as shown in FIG. 8 without disposing a separate gas diffusion layer on the positive electrode layer.

The manufactured lithium-air battery has a structure in which the cells are arranged at the upper and lower portions, respectively, based on the bent central portion. One cell is 3 cm wide and 1 cm long, and has an area of 3 cm ² Therefore, the total cell area of the lithium-air battery is 6 cm ² (= 3 cm × 1 cm × 2).

Comparative Example 2: Fabrication of a conventional lithium-air battery

The lithium-air battery according to Comparative Example 2 was manufactured in the same manner as the lithium-air battery of Comparative Example 1, except that the gas diffusion layer was disposed between the bent positive electrode layers.

The lithium-air battery according to Comparative Example 2 is manufactured by disposing a gas diffusion layer on the positive electrode layer, and then bending the positive electrode layer, the electrolyte membrane and the negative electrode metal layer as shown in FIG. 9 so that the positive electrode layer surrounds at least three surfaces of the gas diffusion layer. did. At this time, as the gas diffusion layer, carbon paper having a weight per unit area of 4.2 mg/cm ² was used.

Example 1: Fabrication of Lithium-Air Battery

(Production of anode layer)

A positive electrode layer was prepared in the same manner as in Comparative Example 1.

(Production of electrolyte membrane)

An electrolyte membrane was prepared in the same manner as in Comparative Example 1.

(Production of gas diffusion layer)

A plurality of carbon fibers (graphite fibers manufactured by Fiber Glast) having a length of 0.25 inches and a diameter of 7 μm are disposed on the positive electrode layer.

A plurality of carbon fibers disposed on the positive electrode layer are pressed with a predetermined pressure. Thus, the plurality of carbon fibers are inserted and fixed in the insertion groove of the positive electrode layer.

The gas diffusion layer is fixed to the anode layer without a binder, and has a weight per unit area of 0.2 mg/cm ² .

(Production of lithium-air batteries)

In the lithium-air battery according to Example 1, as in Comparative Example 2, after arranging the gas diffusion layer on the positive electrode layer, as shown in FIG. 9, the positive electrode layer and the electrolyte membrane so that the positive electrode layer surrounds at least three surfaces of the gas diffusion layer. and bending the cathode metal layer.

Example 2: Fabrication of Lithium-Air Battery

The lithium-air battery according to Example 2 was manufactured in the same manner as the lithium-air battery of Example 1, except for the weight per unit area of the gas diffusion layer. In the lithium-air battery according to Example 2, the gas diffusion layer is fixed to the positive electrode layer without a binder, and the weight per unit area is 0.05 mg/cm ² .

Example 3: Fabrication of lithium-air batteries

The lithium-air battery according to Example 3 was manufactured in the same manner as the lithium-air battery of Example 1, except for the weight per unit area of the gas diffusion layer. In the lithium-air battery according to Example 3, the gas diffusion layer is fixed to the positive electrode layer without a binder, and the weight per unit area is 0.03 mg/cm ² .

Charging/discharging characteristics evaluation

Discharge capacities of the lithium-air batteries prepared in Example 1 and Comparative Example 1 were measured at 80° C. and 1 atm oxygen atmosphere, and the results are shown in Table 1 and FIG. 15 below.

Since the lithium-air battery has a structure that is bent once, and the positive electrode is disposed on the upper and lower portions of the gas diffusion layer, the weight per unit area of the gas diffusion layer was calculated by dividing the upper and lower positive electrodes in half.

gas diffusion layer
shape per unit area
Weight (mg/cm ² ) energy density
(Wh/kg) Comparative Example 1 doesn't exist 0 112 Comparative Example 2 carbon paper 2.1 632 Example 1 carbon fiber
(no binder) 0.2 744 Example 2 carbon fiber
(no binder) 0.05 820 Example 3 carbon fiber
(no binder) 0.03 827

As shown in Table 1, compared to the lithium-air battery without the gas diffusion layer according to Comparative Example 1, the lithium-air battery with the gas diffusion layer according to Comparative Example 2 increased energy density, but due to the presence of the gas diffusion layer, per unit area It can be seen that the weight increased by 2.1 mg/cm ² .

Unlike the lithium-air battery according to Comparative Example 2, the lithium-air battery according to Example 1 uses carbon fibers without a binder as the gas diffusion layer, so the weight per unit area of the gas diffusion layer is the weight per unit area of the gas diffusion layer of Comparative Example 2 It can be confirmed that the energy density can be increased while decreasing to less than 1/10 of

In addition, it can be seen that the lithium-air batteries according to Examples 2 and 3 can further increase the energy density while further reducing the weight per unit area of the gas diffusion layer than in Example 1

In the above, the preferred embodiment according to the present invention has been described with reference to the drawings and examples, but this is only an example, and various modifications and equivalent other embodiments are possible therefrom by those of ordinary skill in the art. will be able to understand Accordingly, the protection scope of the present invention should be defined by the appended claims.

1, 1B, 1C, 1D, 1E: metal air cells
11: cathode metal layer 12: electrolyte membrane
13: anode layer 131: first surface
132: second surface 133: insertion groove
14, 14A, 14B, 14C, 14D, 14E: gas diffusion layer
141, 151: carbon fiber 140: first carbon fiber layer
150: second carbon fiber layer

Claims (20)

at least one positive electrode layer using oxygen as an active material and having a first surface and a second surface opposite to the first surface;
a gas diffusion layer disposed on the first surface of the anode layer and including a plurality of carbon fibers;
an electrolyte membrane disposed on the second surface of the anode layer; and
Including; a negative electrode metal layer disposed on the electrolyte membrane;
The anode layer has a plurality of insertion grooves in which some regions of the plurality of carbon fibers are inserted on the first surface,
The partial region of the plurality of carbon fibers extends in the same direction as the extending direction of the insertion groove, metal-air battery. According to claim 1,
The average depth of the insertion groove is 20% to 60% of the diameter of the carbon fiber, metal-air battery. According to claim 1,
The average width of the insertion groove is 80% to 100% of the diameter of the carbon fiber, metal-air battery. According to claim 1,
The average length of the insertion groove is 3 mm or more, metal-air battery. According to claim 1,
The average spacing between the insertion grooves is 30 μm to 1000 μm, a metal-air battery. According to claim 1,
The carbon fiber has a diameter of 5 μm to 10 μm, a metal-air battery. According to claim 1,
The weight per unit area of the gas diffusion layer is 0.5 mg/cm ² hereinafter, a metal-air battery. 8. The method of claim 7,
The weight per unit area of the gas diffusion layer is 0.007 mg/cm ² Ideal, metal-air batteries. According to claim 1,
The gas diffusion layer,
a first carbon fiber layer having a plurality of carbon fibers disposed on the anode layer;
and a second carbon fiber layer disposed on the first carbon fiber layer and having a plurality of carbon fibers extending in a direction crossing the extending direction of the carbon fibers of the first carbon fiber layer. According to claim 1,
The gas diffusion layer, as a layer, is bent to face each other, a metal-air battery. 11. The method of claim 10,
The gas diffusion layer has a plurality of carbon fiber layers comprising a plurality of carbon fibers, wherein the plurality of carbon fiber layers is four or less layers. According to claim 1,
The gas diffusion layer is partially disposed on the anode layer,
The anode metal layer, the electrolyte membrane and the anode layer are bent over the gas diffusion layer so that the anode layer is in contact with three surfaces of the gas diffusion layer, and one side of the gas diffusion layer is exposed to the outside, a metal-air battery . disposing a plurality of carbon fibers on one surface of the positive electrode layer using oxygen as an active material; and
Forming a gas diffusion layer by pressing the plurality of carbon fibers toward the anode layer so that a partial region of the plurality of carbon fibers is inserted into one surface of the anode layer to form an insertion groove;
The insertion groove extends in the same direction as the extension direction of the partial regions of the plurality of carbon fibers, the metal-air battery manufacturing method. 14. The method of claim 13,
In the pressing step of the carbon fiber,
The carbon fiber is pressed to the positive electrode layer so that the average depth of the insertion groove is 20% to 60% of the diameter of the carbon fiber, the metal-air battery manufacturing method. 14. The method of claim 13,
In the pressing step of the carbon fiber,
The carbon fiber is pressed so that the average width of the insertion groove is 80% to 100% of the diameter of the carbon fiber, the metal-air battery manufacturing method. 14. The method of claim 13,
In the step of disposing the carbon fiber,
A method for manufacturing a metal-air battery, wherein a plurality of carbon fibers are disposed such that the average spacing between the carbon fibers is 30 μm to 1000 μm. 14. The method of claim 13,
The weight per unit area of the gas diffusion layer is 0.5 mg/cm ² The following, a metal-air battery manufacturing method. 18. The method of claim 17,
The weight per unit area of the gas diffusion layer is 0.007 mg/cm ² The above, a method for manufacturing a metal-air battery. A gas diffusion layer comprising a plurality of carbon fibers disposed on one surface of a positive electrode layer using oxygen as an active material,
A partial region of the plurality of carbon fibers is inserted into one surface of the positive electrode layer,
The partial region of the plurality of carbon fibers extends in the same direction as the extending direction of the insertion groove, a gas diffusion layer for a metal-air battery. 20. The method of claim 19,
The gas diffusion layer does not contain a binder, a gas diffusion layer for a metal-air battery.

Images